Videos of Cells and Embryos
In the videos on this page microtubules are labeled with a probe consisting of three GFPs in a row fused to the microtubule-binding domain from human Ensconsin, and also with Histone H2B fused to mCherry to mark the chromosomes.
The first video is a side view of a 16-cell embryo, with the animal pole to the right and vegetal to the left; the embryo consists of four small cells at the vegetal end, called micromeres, their four large sisters the macromeres, and eight mesomeres of the animal hemisphere.
Embryonic mitosis in urchins
November 17, 2013
Species:
Strongylocentrotus purpuratus
Frame rate:
20 sec/frame @ 15 fps = 250-fold time-lapse
Points of interest:
mitosis; spindle assembly; chromosome congression
What’s glowing:
3xGFP-EMTB (Ensconsin Microtubule Binding Domain) labels microtubules, mCherry-Histone H2B labels chromosomes
Optics:
CARV spinning disk confocal; 60x; projection of 15-20 1-µm sections.
Filmed by:
George von Dassow & Bill Bement
More like this:
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The second video starts at the 28-cell stage, looking straight down the vegetal pole. The micromeres divide later than the rest of the embryo, and when they do, they divide unequally to make small micromeres and large micromeres. The small micromeres do not divide again within the time span covered by this movie; they divide only once more during embryogenesis.
Regardless of the cell arrangement within the embryo, the remarkable thing in these movies is that they dramatize the extent to which mitosis involves complete reorganization of the cell. The other two movies below have the colors reversed to highlight chromosome behavior during mitosis rather than the microtubules; there are several dozen of these strands, which presumably might get tangled up either on the spindle or while decondensed during interphase, and yet they appear to snap into configuration within mere minutes, condensing out of formless glow and hooking up to the spindle, then moving poleward along it before decondensing again to replicate.
